The invention relates to a method for controlling a shift process of an automatic gearbox in a vehicle with an internal combustion engine as the engine, a controller for carrying out the method as well as a vehicle.
In order to reduce the load on a driver, in particular of large commercial vehicles, it is generally known to fit the vehicle with an automatic gearbox. With this, a target gear of the gearbox is determined depending on diverse parameters and a shift command is automatically carried out on reaching specified shift conditions. The criterion for such an automatic shift process is in particular the most fuel efficient possible operation of the vehicle.
With a known method for controlling a shift process of an automatic gearbox in a vehicle with an internal combustion engine as the engine (DE 198 54 254 A 1), a shift strategy is specified in a controller, with which the behaviour of the engine following any shift process into a target gear is continuously determined in advance on the basis of current detected vehicle dynamic and/or vehicle specific and/or engine specific actual values. An engine revolution rate, an output revolution rate of the gearbox, an accelerator pedal position, a brake pedal position and a vehicle speed are used here as actual values for the calculation of such a prediction result.
Furthermore, an accelerator pedal speed, a current vehicle mass and a road gradient can be taken into account here. Taking account of said prediction results, adapted shift thresholds are determined and specified as upshift thresholds or downshift thresholds, in particular for a fuel efficient shift, wherein a control command for a corresponding automatic shift process is output after exceeding such a shift threshold. Specifically, basic limit revolution rate ranges, which are variable in terms of their limits and can be adapted to the respective current conditions, are specified as shift thresholds here.
As can be seen, the decision as to whether a shift process will be fuel efficient or not, and as a result whether any fuel savings can be achieved, depends on how accurately a predicted determination of the behaviour of the engine can be determined, in particular of a build-up of torque following any shift process into a target gear.
Furthermore, a control method for an automatic gearbox is known (DE 10 2005 050 479 A1), with which the behaviour of the engine with regard to the predicted engine revolution rate following a shift into a target gear is likewise predictively calculated prior to a shift process. Said calculated engine revolution rate is compared with a downshift threshold and an automatic upshift into the target gear will only be implemented in the event of exceeding such a downshift threshold. In a similar known control method (DE 601 02 962 T2), a precalculation of an engine revolution rate is likewise carried out for a possible target gear and an upshift process is only implemented if a maximum permissible engine revolution rate will not be exceeded thereby.